As the critical dimensions of integrated circuits become smaller and smaller, it may become increasingly difficult to make a metal interconnection, e.g., an aluminum interconnection, for use in a semiconductor device. In forming a metal interconnection, it may be desirable to completely fill a contact hole, which is a connection between a lower conductive layer and an upper aluminum interconnection, or a via hole, which is a connection between lower and upper aluminum interconnections, with an interconnection material.
To fill the contact hole or via hole (hereinafter, referred to as a “contact hole” or simply as a “hole”) with aluminum, various process techniques have been developed to attempt to obtain superior electrical characteristics and filling characteristics. In a highly integrated memory device, an aspect ratio of a contact hole may become higher during a deposition process of forming a metal interconnection having a critical dimension of 0.25 μm or less. Thus, physical vapor deposition (PVD) such as a sputtering process may not be amenable for use during the deposition process. Efforts have been made to develop various methods of forming an aluminum interconnection using chemical vapor deposition (CVD) that can have superior step coverage characteristics in comparison with PVD. In particular, preferential metal deposition (PMD) has been developed to selectively form an aluminum thin layer only in a contact hole by CVD and depositing an aluminum layer outside the contact hole by PVD.
FIGS. 1A and 1B are cross-sectional views illustrating a conventional method of fabricating a metal interconnection of a semiconductor device by PMD. Referring to FIG. 1A, first, a dielectric layer pattern, such as an interlevel dielectric pattern 8, for defining a contact hole 4, is formed on a semiconductor substrate 2. Next, an ohmic metal layer 12 and a barrier metal layer 14 are sequentially formed on the interlevel dielectric layer pattern 8. Thereafter, an anti-nucleation layer 16 is formed on the interlevel dielectric layer 8, so that only a portion of the barrier metal layer 14, which is formed along the sidewalls and bottom of the contact hole 4, is exposed. Next, an aluminum thin layer 18 is selectively formed in the contact hole 4 using CVD, whereby an aluminum precursor is hardly deposited outside the contact hole 4. As a result, such selective deposition of aluminum can have higher step coverage characteristics than a blanket deposition of aluminum. Thus, the PMD process may be suitable for a process of filling a contact hole of a small size with aluminum.
However, it may be almost inevitable that particles 20 are generated during various processes, such as the selective CVD of forming the aluminum thin layer 18 in the contact hole 4, an etching process, and/or a deposition process. Around the particles 20 and/or the circumference of the contact hole 4, the anti-nucleation layer 16 may be poorly deposited so that the barrier metal layer 14 may be incompletely covered with the anti-nucleation layer 16. Therefore, a monocrystalline growth portion 22 may be formed around the particles 20 and/or the circumference of the contact hole 4, due to undesired growth of aluminum. In general, the undesired growth of aluminum may be caused around the particles 20 and/or the circumference of the contact hole 4 in which a portion of the barrier metal layer 14 is not evenly covered with the anti-nucleation layer 16. Thus, the barrier metal layer 14 may be exposed through the anti-nucleation layer 16. This undesired growth may be due to a difference between the selective aluminum growth characteristics of the barrier metal layer 14 and the anti-nucleation layer 16. That is, aluminum may be single-crystal grown only in one direction on the barrier metal layer 14 that has better selective aluminum growth characteristics than the anti-nucleation layer 16, thereby forming the monocrystalline growth portion 22. After forming the monocrystalline growth portion 22, if the blanket deposition of aluminum is performed using PVD to form an aluminum interconnection 24, undesired aluminum growth portions 26 may be present on the aluminum interconnection 24 as illustrated in FIG. 1B, which may cause a bridging phenomenon in a multilevel metal interconnection and/or other undesirable effects.